Australia is the fourth cheapest country in the world in which to fly, new research has suggested, with airfares costing just $US12.20 ($A13.06) per 100km. Among, the western countries, it is the first beating Spain at number 4 and US at number 6.

But, it is India that tops the list as the the cheapest country in the world in which to fly - airfares costing just $US10.36 ($A11.17) per 100km. It is followed by Malaysia and South Africa, which claim second and third spots respectively, ahead of Australia.

By comparison, the most expensive country in the world in which to board a flight is Finland, where you'll pay $US138.90 ($A148.72) per 100km – more than 13 times as much. The second most expensive country is Switzerland, followed by Lithuania, Austria and Estonia.

The study, by the travel website GoEuro.com, compared average fares – not just for flights, but also train and bus journeys - in 51 countries across five continents.

The cheapest country for bus travel was found to be Egypt, where journeys typically cost $US1.88 ($A2.01) per 100km.

South Africans enjoy the cheapest travel overall, it claims, with airfares costing $US11.63 ($A12.45) per 100km, and the country having the most cost-effective rail network - with train trips priced at $US1.88 ($A2.01) per 100km.

It outranked Albania which came as the second cheapest country to travel overall, according the Transportation Price Index, followed by Malaysia and Thailand in equal third spot.

Australia was ranked as the 25th cheapest country for travel overall. Unsurprisingly, Spain, Germany, US and France out-ranked Australia in 11, 17, 22 and 23 spots respectively.